next-intl has an open redirect vulnerability
Impact
Applications using the next-intl middleware with localePrefix: 'as-needed' could construct URLs where path handling and the WHATWG URL parser resolved a relative redirect target to another host (e.g. scheme-relative // or control characters stripped by the URL parser), so the middleware could redirect the browser off-site while the user still started from a trusted app URL.
Patches
The problem has been patched, please update to next-intl@4.9.1.
Credits
Many thanks to Joni Liljeblad from Oura for responsibly disclosing the vulnerability and for suggesting the fix.
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| npm package | next-intl | < 4.9.1 | 4.9.1 |
References
- https://github.com/amannn/next-intl/security/advisories/GHSA-8f24-v5vv-gm5j
- https://nvd.nist.gov/vuln/detail/CVE-2026-40299
- https://github.com/amannn/next-intl/pull/2304
- https://github.com/amannn/next-intl/commit/1c80b668aa6d853f470319eec10a3f61e78a70e6
- https://github.com/amannn/next-intl
- https://github.com/amannn/next-intl/releases/tag/v4.9.1
- CVSS vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N- Weakness (CWE)
CWE-601- Platform
- npm
- Package
next-intl- Disclosed
- 10.04.2026
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-8f24-v5vv-gm5j - CC BY 4.0
Vulnerability history: next-intl
All published vulnerabilities of this package (npm package), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 2
- First → latest
- 04.2026 05.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- Medium 2
Disclosures per year
- 2026: 2
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next-intl has an open redirect vulnerability this entry
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